This invention relates to a fluid flow control device that combines the functions of pressure regulation and selectable flow control. That is, the device regulates the pressure at the outlet to a predetermined value and it responds to a suitable control signal to permit or prevent fluid flow. The device will be referred to herein as a regulator valve. The device is particularly suitable for use on agricultural irrigation machines, although it is not limited to this use.
Agricultural irrigation machines of the type known as center pivot machines have a main pipeline supported on movable towers for rotation about an inner end of the pipeline. Water (with or without added fertilizer, herbicide, insecticide etc.) is supplied to the fixed, inner end of the pipeline. Sprinkler heads are mounted at intervals along the length of the pipeline for distributing the water. The sprinkler heads can be mounted more or less directly to the pipeline or at the end of tubular drop mechanisms that suspend the sprinkler heads just above or within the crop canopy. In either case the flow rate of water through a sprinkler head is dependent on the hydraulic pressure at the inlet of the sprinkler head. That pressure can vary along the length of the pipeline due to friction losses in the pipe and undulations in the local terrain. When it is critical to control the flow rate through a sprinkler head a pressure regulator is placed between the pipeline and the sprinkler heads to assure a known hydraulic pressure at the sprinkler head""s inlet, regardless of its location along the length of the pipeline or undulations in the local terrain. A typical pressure regulator of this type is shown in U.S. Pat. No. 4,543,985.
In some applications it may be also desirable to be able to turn individual sprinkler heads on or off, in addition to controlling the pressure seen by the inlet of the head. Examples where this would be advantageous include a center pivot machine having a swing span pivotably connected to the moving end of the pipeline. The swing span swings into the corners of a field to irrigate portions that would otherwise be missed by the circular pattern covered by the main pipeline. The swing span folds in when the main pipeline is opposite an edge of the field and swings out into a corner. U.S. Pat. Nos. 4,011,990 and 5,695,129 describe such a machine. The main pipeline may stop while the swing span irrigates the corner portion. In that case, it would be desirable to turn off the main pipeline sprinklers. The swing span sprinklers need to be off when the swing span is not irrigating a corner. Another example where on-off control is desirable is where field conditions are known to vary from one location to another and the irrigation machine is programmed to apply water and/or chemicals at differing rates dependent on these known field conditions.
While prior art pressure regulators provide adequate pressure regulation, none of the known regulators incorporates a selectable on-off feature. The present invention adds this capability to furnish a combined regulator and control valve.
The present invention concerns a regulator valve for regulating fluid pressure and selectably turning flow on or off. The valve has a housing defining a hollow enclosure with inlet and outlet ends. Inside the housing is a seal member and a spool assembly which are movable relative to one another. The spool assembly has a passage through it and is sealed to the housing such that fluid flow from the inlet to the outlet must go through the passage. When the spool assembly engages the seal member the passage is closed and flow through the device is prevented. The spool assembly is exposed to fluid pressure at the outlet end to bias the spool assembly toward the seal member. A spring engages the housing and the spool assembly to bias the spool assembly away from the seal. Balancing of the spring force and fluid pressure controls the separation between the seal member and the passage in the spool assembly, thereby governing the pressure at the outlet of the regulator valve.
The spool assembly includes first and second plungers each connected to first and second flexible diaphragms, respectively. Each diaphragm contacts the inner wall of the housing in sealing engagement. The diaphragms and plungers, together with the housing, define an expansion chamber. A port provides fluid communication to the expansion chamber. Pilot pressure introduced into the expansion chamber biases the first plunger toward the seal member. The pilot pressure is sufficient to overcome the spring force and press the first plunger against the seal member, thereby closing the passages through the plungers and stopping flow through the device. Release of the pilot pressure in the expansion chamber allows the flow to resume under the normal balance of forces on the spool assembly. Pilot pressure may advantageously be taken from the main pipeline under the control of a solenoid valve or it may be separately supplied pneumatic pressure.